The present invention relates to a device for protecting a fuel tank made of synthetic resin from heat of a muffler and an exhaust pipe in an exhaust system of an automotive engine and from fire on roads.
Plastic fuel tanks are easily deformed by fire and heat, Japanese Patent Laid Open No. 57-140226 discloses a fuel tank, a body of which is covered with heatproof material to improve its heatproof and fireproof characteristics. In accordance with another means for protecting the tank from heat, a part of the exhaust system such as a muffler is covered with a plate for intercepting the heat. For example, in a device shown in FIG. 5, a muffler 2 is disposed under a car body 1 adjacent a fuel tank 3. A heat cutoff plate 4 encloses a main part of the muffler 2 to prevent the heat of the muffler from affecting the tank 3. In FIG. 6 showing another stucture of the tank and an exhaust pipe, a tank 3a comprises a deep portion and a shallow portion forming an indentation on the bottom thereof. An exhaust pipe 5 is disposed to pass the indentation under the shallow portion. The heat cutoff plate 4 is so placed as to surround the exhaust pipe in a space between the bottom of the shallow portion and the exhaust pipe.
However, the heat cutoff plate 4 acts to intercept only the heat of the exhaust system. Accordingly, when a fire breaks out in the exhaust system as a result of overheating, or breaks out on the road, the cutoff plate 4 can not prevent the tank from the flames, so that the flames touch side walls of the tanks 3 and 3a and the bottom of the shallow portion as shown by arrows in FIGS. 5 and 6. The flames heat the walls of the tank thereby deforming them, and in extreme cases, holes are formed on the walls. Especially, the side walls above the level of the fuel F such as gasoline are heated earlier than the lower portions of the side walls, because the inside of the upper side walls do not contact the fuel. In addition, the tank, which is made of synthetic resin, which has low heatproof characteristics, could lead to serious accidents.